Collagen is a protein that is distributed to almost all tissues of the body including the skin, bone and cartilage, and is well known to play important functions such as maintaining structures of tissues and organs by providing scaffolds for cells. Meanwhile, collagen is a bioabsorbable material that is decomposed by collagenases secreted from fibroblasts and collagenases present in phagocytes. Collagen is considered to be useful as a biomaterial because it is a biocompatible and bioabsorbable material as described above. Thus far, collagen has been used as a biomaterial for covering wounded skin and is reported to improve healing (Non-Patent Documents 1 and 2).
Forty percent of total collagen exists in the skin, and 70% or more of the dry weight of the skin and tendon is collagen; thus, collagen is important for developing artificial skin. It is applied as a useful material for cell and organ culture techniques, which gives great expectation in its applications in the booming field of regeneration medicine. It has been also pointed out that collagen (type II collagen) may be used to suppress articular rheumatism by oral intake (Non-Patent Documents 3 and 4). As a source material for such collagen, those derived from tissues of large non-human animals such as pigs and cows have been mainly used.    [Non-Patent Document 1] Surg. Forum, 10, 303 (1960)    [Non-Patent Document 2] J. Surg. Res., 10, 485-491 (1970)    [Non-Patent Document 3] Lancet, 342, 799 (1993)    [Non-Patent Document 4] Science, 261, 1727-1730 (1993)    [Patent Document 1] Japanese Patent Application Kokai Publication No. (JP-A) H10-179169 (unexamined, published Japanese patent application)